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Actually, Mars Direct includes no LEO or GEO space assets.  You launch tin cans directly from the Earth to Mars, at a lower delta-V (energy/fuel) cost than the Earth-Moon trip, which gives you the infrastructure for colonization.

Sorta right.  As long as you're shipping supplies from the Moon to LEO (probably oxygen for propellant tanks), it'll reduce Earth-Mars trip costs a bit.  Going from LEO to the Moon, though, takes more delta-V as going from LEO to Mars, and going from LEO to Lunar orbit takes the same delta-V as going from LEO to Mars.  Net, though, it won't reduce them much.

Sorta wrong.  The delta-V from Mars to the Lunar surface is 9.4 km/s; the delta-V from Earth to the Lunar surface is 15.0 km/s.    If it can't be produced locally, and can be procured from Mars at a competitive manufacturing cost to Earth, it's cheaper to import from Mars than the Earth.

Agriculturally, the Moon is useless, because the 600+ hour day-night cycle just can't support plants, and artificial lighting is far, far too energy intensive -- you need a lot (because photosynthesis is so inefficient), and you lose a lot in the electrcity-to-light conversion.  Check the Internet as to how much electricity you need to grow pot indoors; the amount is truly prohibitive unless you have a lot of extra power-generating capacity around.  Easy manufacture of solar panels on the Moon won't alleviate this, since with current technology solar panel manufacture is a net energy sink; we're talking lots of nuclear reactors to replace the Sun.

The delta-v to move mass from Earth to a LEO agricultural facility is 9.0 km/s, and then 6.0 to move it from there to Earth.  The delta-V cost to move mass from the Moon to LEO is on the order of 2.5 km/s, if my math's right (anybody feel free to correct this).  The result is that the fraction of the molecules turned into food in a LEO station takes a delta-V of 8.5 to move from the Moon to Earth, and the fraction lifted from Earth takes 15.0.  The comparative fractions depend on how much hydrogen (that is, polar crater water) there is on the Moon to ship to LEO; nitrogen, potassium, and any hydrogen deficit will have to be shipped from Earth.  Plus, you'll have to build the LEO agricultural colony -- you'll get lots of cheap iron from the Moon if you have enough water, otherwise you'll have to ship iron from Earth to LEO or hydrogen from Earth to the Moon to extract lunar iron.

Now, the numbers using Mars as the agricultural colony look somewhat worse to start -- the net Earth-Mars-Moon delta-V is 22.6 km/sec, and the Mars-to-Moon fraction is 9.4 km/sec.  But Mars is definitely richer in water than the Moon, and it might have enough nitrate deposits, so that the only necessary import would be potassium.

So, the variables work out like this: if there is not enough concentrated water in the lunar polar craters, a Mars colony might be a lower-cost provider of food, water, and hydrogen for a lunar colony than the Earth, but probably not by much.

THE REAL BOTTOM LINE

Agriculture on Mars to feed people on Mars is going to be cheaper than any way of growing food on or importing food to the Moon.  You need to import a minimum of nitrates and phosphorus to the Moon in any case, and you may need to import nitrates and phosphorus to Mars -- but for Mars, it takes less delta-V from Earth, and is thus cheaper.  For the Moon, you additionally will either need more imported power generators for artificial light or spend energy shipping carbon, hydrogen, and oxygen to and from space.  Thus, of the core basics of human existence (air, water, shelter, food), Mars provides at a minimum equal capacity on the first three and superior capacity on the fourth.

If we're just going on Apollo-style look-and-see missions, then the Moon makes more sense because it's closer.  If we're going for long term semi-self-sustaining facilities, Mars is the better choice.